1. Field of the Invention
This invention concerns corrosion monitoring, in general. More specifically, it relates to a system for monitoring the effectiveness of a buried structure that is under cathodic protection for reducing corrosion.
2. Description of the Prior Art
Heretofore, there have been various proposals for making measurements or determinations relating to the rate of corrosion of a metal object or the like that is subjected to corrosive conditions. Thus, there are U.S. Pats. such as those to Marsh et al, No. 3,066,082, Nov. 27, 1962; Estes et al, No. 3,209,255, Sept. 28, 1965; Kanno et al, No. 4,130,464, Dec. 19, 1978; and Tejfalussy et al, No. 4,155,814, May 22, 1979.
The Marsh et al patent does deal with determining conditions of protective coatings on a pipeline. However, it makes use of a specimen pipe that must be as similar as possible to a corresponding section of the pipeline. And, in addition, the specimen is separate and is electrically unconnected to the pipeline which is done in order to avoid complications relating to cathodic protection currents to which the pipeline is subjected. The applicant's invention, on the other hand, is a simple system that makes use of the cathodic protection current flow itself. And, it measures the quantity of current over an extended period of time in order to determine the effectiveness of the protection at a given location on a pipeline.
The Estes et al patent merely discloses a particular type of current integrator. It employs a fritted disc in order to obtain osmotic current flow, and it basically acts as a coulometer per se which may be used in various ways.
The Kanno et al patent deals with a relatively complicated electronic circuit arrangement for evaluating corrosion rates of metals and, consequently, is not relevant to the applicant's invention.
The Tejfalussy et al patent provides for setting up a galvanic action circuit arrangement. And, it employs a plurality of electrodes situated near a metallic object that is to have the corrosion investigation thereof carried out.
Thus, it is an object of this invention to provide a relatively simple yet highly effective system for monitoring the current flow that relates to a buried structure which is under cathodic protection.